payment-integration

SKILL.md

Payment Integration

Production-proven payment processing with SePay (Vietnamese banks), Polar (global SaaS), Stripe (global infrastructure), Paddle (MoR subscriptions), and Creem.io (MoR + licensing).

When to Use

Payment gateway integration (checkout, processing)

Subscription management (trials, upgrades, billing)

Webhook handling (notifications, idempotency)

QR code payments (VietQR, NAPAS)

Software licensing (device activation)

Multi-provider order management

Revenue splits and commissions

Platform Selection

Platform
Best For

SePay
Vietnamese market, VND, bank transfers, VietQR

Polar
Global SaaS, subscriptions, automated benefits (GitHub/Discord)

Stripe
Enterprise payments, Connect platforms, custom checkout

Paddle
MoR subscriptions, global tax compliance, churn prevention

Creem.io
MoR + licensing, revenue splits, no-code checkout

Quick Reference

SePay

references/sepay/overview.md - Auth, supported banks

references/sepay/api.md - Endpoints, transactions

references/sepay/webhooks.md - Setup, verification

references/sepay/sdk.md - Node.js, PHP, Laravel

references/sepay/qr-codes.md - VietQR generation

references/sepay/best-practices.md - Production patterns

Polar

references/polar/overview.md - Auth, MoR concept

references/polar/products.md - Pricing models

references/polar/checkouts.md - Checkout flows

references/polar/subscriptions.md - Lifecycle management

references/polar/webhooks.md - Event handling

references/polar/benefits.md - Automated delivery

references/polar/sdk.md - Multi-language SDKs

references/polar/best-practices.md - Production patterns

Stripe

references/stripe/stripe-best-practices.md - Integration design

references/stripe/stripe-sdks.md - Server SDKs

references/stripe/stripe-js.md - Payment Element

references/stripe/stripe-cli.md - Local testing

references/stripe/stripe-upgrade.md - Version upgrades

External: https://docs.stripe.com/llms.txt

Paddle

references/paddle/overview.md - MoR, auth, entity IDs

references/paddle/api.md - Products, prices, transactions

references/paddle/paddle-js.md - Checkout overlay/inline

references/paddle/subscriptions.md - Trials, upgrades, pause

references/paddle/webhooks.md - SHA256 verification

references/paddle/sdk.md - Node, Python, PHP, Go

references/paddle/best-practices.md - Production patterns

External: https://developer.paddle.com/llms.txt

Creem.io

references/creem/overview.md - MoR, auth, global support

references/creem/api.md - Products, checkout sessions

references/creem/checkouts.md - No-code links, storefronts

references/creem/subscriptions.md - Trials, seat-based

references/creem/licensing.md - Device activation

references/creem/webhooks.md - Signature verification

references/creem/sdk.md - Next.js, Better Auth

External: https://docs.creem.io/llms.txt

Multi-Provider

references/multi-provider-order-management-patterns.md - Unified orders, currency conversion

Scripts

scripts/sepay-webhook-verify.js - SePay webhook verification

scripts/polar-webhook-verify.js - Polar webhook verification

scripts/checkout-helper.js - Checkout session generator

Key Capabilities

Platform
Highlights

SePay
QR/bank/cards, 44+ VN banks, webhooks, 2 req/s

Polar
MoR, subscriptions, usage billing, benefits, 300 req/min

Stripe
CheckoutSessions, Billing, Connect, Payment Element

Paddle
MoR, overlay/inline checkout, Retain (churn prevention), tax

Creem.io
MoR, licensing, revenue splits, no-code checkout

Implementation

See references/implementation-workflows.md for step-by-step guides per platform.

General flow: auth → products → checkout → webhooks → events